Imaging regulatory T cell dynamics and CTLA4-mediated suppression of T cell priming

Foxp3(+) regulatory T cells (Tregs) maintain immune homoeostasis through mechanisms that remain incompletely defined. Here by two-photon (2P) imaging, we examine the cellular dynamics of endogenous Tregs. Tregs are identified as two non-overlapping populations in the T-zone and follicular regions of the lymph node (LN). In the T-zone, Tregs migrate more rapidly than conventional T cells (Tconv), extend longer processes and interact with resident dendritic cells (DC) and Tconv. Tregs intercept immigrant DCs and interact with antigen-induced DC: Tconv clusters, while continuing to form contacts with activated Tconv. During antigen-specific responses, blocking CTLA4-B7 interactions reduces Treg-Tconv interaction times, increases the volume of DC: Tconv clusters and enhances subsequent Tconv proliferation in vivo. Our results demonstrate a role for altered cellular choreography of Tregs through CTLA4-based interactions to limit T-cell priming

Modulation de la réponse immunitaire par les immunoglobulines intraveineuses : effets sur la polarisation, la pathogénicité et le trafic des lymphocytes T

Dysregulated activation of T cells leads to pathogenic immune response to self-antigens. Despite an increasing use of high dose therapy of intravenous gammaglobulin (IVIg) in the treatment of T-cell and autoantibody-mediated inflammatory and autoimmune diseases, comprehension of the mechanisms underlying its therapeutic benefit has remained a major challenge. Particularly, the effect of IVIg in T cell mediated autoimmune conditions remains unexplored. I have investigated the effect of high dose IVIg on T cell polarization using actively induced experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune condition. IVIg inhibits the differentiation of naïve CD4 T cells into effector subsets (Th1 and Th17 cells) and concomitantly induces an expansion of Foxp3+ regulatory cells. IVIg decreases the tissue damaging potential of pathogenic T cells by down regulating GM-CSF and podoplanin. Additionally, IVIg circumvents the neuronal damage by inhibiting the infiltration of CD4 T lymphocytes to the central nervous system by restraining their egress from the DLN through S1P-S1P1-mTOR pathway. Intriguingly and contrary to the current arguments, the inhibitory FcγRIIB and sialylation of IgG are dispensable for IVIg-mediated reciprocal modulation of effector and regulatory CD4 subsets. Altogether, therapeutic benefit of IVIg in EAE involves shifting the balance from Th17/Th1 towards Treg, down-regulating encephalitogenic mediators and inhibition of T cell trafficking to the target organ.L'activation dérégulée de lymphocytes T conduit à une réponse immune délétère envers les antigènes du soi. Malgré une utilisation croissante de doses élevées d'IVIg pour traiter les maladies auto-immunes, la compréhension des mécanismes sous-jacents aux bénéfices thérapeutiques demeure un enjeu majeur. En effet, les effets des IVIg restent inexplorés dans le cadre des maladies auto-immunes associées aux lymphocytes T. J'ai recherché les effets de doses élevées d'IVIg dans la polarisation des lymphocytes T en utilisant le modèle de l'encéphalomyélite auto-immune expérimentale (EAE), une maladie auto-immune associée aux lymphocytes T. Les IVIg inhibent la différenciation des lymphocytes T CD4+ naïfs en sous-populations effectrices (lymphocytes Th1 et Th17) et induisent, de manière concomitante, une prolifération des lymphocytes T Foxp3+. Les IVIg diminuent les effets délétères des lymphocytes T sur les tissus en diminuant l'expression du GM-CSF et de la podoplanine. En outre, les IVIg empêchent la dégénérescence neuronale en inhibant l'infiltrat en lymphocytes T CD4+ dans le système nerveux central (SNC). Ce mécanisme passe par une séquestration de ces lymphocytes dans les ganglions lymphatiques drainants à travers la voie de signalisation S1P-S1P1-mTor. De manière intéressante, et contrairement aux données actuelles, le récepteur inhibiteur FcγRIIB et la sialylation des IVIg ne sont pas indispensables pour la modulation des sous-populations de lymphocytes T CD4+ effecteurs et régulateurs induite par les IVIg. Ainsi, le bénéfice thérapeutique des IVIg dans le modèle de l'EAE implique un déséquilibre de la balance entre les lymphocytes Th17/Th1 et les lymphocytes Trég, au profit des lymphocytes Trég. Ces cellules diminuent l'expression de médiateurs favorisant l'apparition de l'encéphalomyélite et inhibent la migration des lymphocytes T vers l'organe cible

Intervenous immunoglobulins as modulators of immune response (effect on T cell polarisation, pathogenicity and trafficking)

L activation dérégulée de lymphocytes T conduit à une réponse immune délétère envers les antigènes du soi. Malgré une utilisation croissante de doses élevées d IVIg pour traiter les maladies auto-immunes, la compréhension des mécanismes sous-jacents aux bénéfices thérapeutiques demeure un enjeu majeur. En effet, les effets des IVIg restent inexplorés dans le cadre des maladies auto-immunes associées aux lymphocytes T. J ai recherché les effets de doses élevées d IVIg dans la polarisation des lymphocytes T en utilisant le modèle de l encéphalomyélite auto-immune expérimentale (EAE), une maladie auto-immune associée aux lymphocytes T. Les IVIg inhibent la différenciation des lymphocytes T CD4+ naïfs en sous-populations effectrices (lymphocytes Th1 et Th17) et induisent, de manière concomitante, une prolifération des lymphocytes T Foxp3+. Les IVIg diminuent les effets délétères des lymphocytes T sur les tissus en diminuant l expression du GM-CSF et de la podoplanine. En outre, les IVIg empêchent la dégénérescence neuronale en inhibant l infiltrat en lymphocytes T CD4+ dans le système nerveux central (SNC). Ce mécanisme passe par une séquestration de ces lymphocytes dans les ganglions lymphatiques drainants à travers la voie de signalisation S1P-S1P1-mTor. De manière intéressante, et contrairement aux données actuelles, le récepteur inhibiteur FcgRIIB et la sialylation des IVIg ne sont pas indispensables pour la modulation des sous-populations de lymphocytes T CD4+ effecteurs et régulateurs induite par les IVIg. Ainsi, le bénéfice thérapeutique des IVIg dans le modèle de l EAE implique un déséquilibre de la balance entre les lymphocytes Th17/Th1 et les lymphocytes Trég, au profit des lymphocytes Trég. Ces cellules diminuent l expression de médiateurs favorisant l apparition de l encéphalomyélite et inhibent la migration des lymphocytes T vers l organe cibleDysregulated activation of T cells leads to pathogenic immune response to self-antigens. Despite an increasing use of high dose therapy of intravenous gammaglobulin (IVIg) in the treatment of T-cell and autoantibody-mediated inflammatory and autoimmune diseases, comprehension of the mechanisms underlying its therapeutic benefit has remained a major challenge. Particularly, the effect of IVIg in T cell mediated autoimmune conditions remains unexplored. I have investigated the effect of high dose IVIg on T cell polarization using actively induced experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune condition. IVIg inhibits the differentiation of naïve CD4 T cells into effector subsets (Th1 and Th17 cells) and concomitantly induces an expansion of Foxp3+ regulatory cells. IVIg decreases the tissue damaging potential of pathogenic T cells by down regulating GM-CSF and podoplanin. Additionally, IVIg circumvents the neuronal damage by inhibiting the infiltration of CD4 T lymphocytes to the central nervous system by restraining their egress from the DLN through S1P-S1P1-mTOR pathway. Intriguingly and contrary to the current arguments, the inhibitory FcgRIIB and sialylation of IgG are dispensable for IVIg-mediated reciprocal modulation of effector and regulatory CD4 subsets. Altogether, therapeutic benefit of IVIg in EAE involves shifting the balance from Th17/Th1 towards Treg, down-regulating encephalitogenic mediators and inhibition of T cell trafficking to the target organPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Immunomodulation by Intravenous Immunoglobulin: Role of Regulatory T Cells

International audienc

Intravenous Gammaglobulin Inhibits Encephalitogenic Potential of Pathogenic T Cells and Interferes with their Trafficking to the Central Nervous System, Implicating Sphingosine-1 Phosphate Receptor 1–Mammalian Target of Rapamycin Axis

International audienc

Effect of IVIg on human dendritic cell-mediated antigen uptake and presentation: Role of lipid accumulation

International audienc

T-cell calcium dynamics visualized in a ratiometric tdTomato-GCaMP6f transgenic reporter mouse.

Calcium is an essential cellular messenger that regulates numerous functions in living organisms. Here, we describe development and characterization of 'Salsa6f', a fusion of GCaMP6f and tdTomato optimized for cell tracking while monitoring cytosolic Ca2+, and a transgenic Ca2+ reporter mouse with Salsa6f targeted to the Rosa26 locus for Cre-dependent expression in specific cell types. The development and function of T cells was unaffected in Cd4-Salsa6f mice. We describe Ca2+ signals reported by Salsa6f during T cell receptor activation in naive T cells, helper Th17 T cells and regulatory T cells, and Ca2+ signals mediated in T cells by an activator of mechanosensitive Piezo1 channels. Transgenic expression of Salsa6f enables ratiometric imaging of Ca2+ signals in complex tissue environments found in vivo. Two-photon imaging of migrating T cells in the steady-state lymph node revealed both cell-wide and localized sub-cellular Ca2+ transients ('sparkles') as cells migrate

T-cell calcium dynamics visualized in a ratiometric tdTomato-GCaMP6f transgenic reporter mouse.

Calcium is an essential cellular messenger that regulates numerous functions in living organisms. Here, we describe development and characterization of 'Salsa6f', a fusion of GCaMP6f and tdTomato optimized for cell tracking while monitoring cytosolic Ca2+, and a transgenic Ca2+ reporter mouse with Salsa6f targeted to the Rosa26 locus for Cre-dependent expression in specific cell types. The development and function of T cells was unaffected in Cd4-Salsa6f mice. We describe Ca2+ signals reported by Salsa6f during T cell receptor activation in naive T cells, helper Th17 T cells and regulatory T cells, and Ca2+ signals mediated in T cells by an activator of mechanosensitive Piezo1 channels. Transgenic expression of Salsa6f enables ratiometric imaging of Ca2+ signals in complex tissue environments found in vivo. Two-photon imaging of migrating T cells in the steady-state lymph node revealed both cell-wide and localized sub-cellular Ca2+ transients ('sparkles') as cells migrate

Cxcl17-/- mice develop exacerbated disease in a T cell-dependent autoimmune model.

CXCL17 is a homeostatic chemokine in the mucosa known to chemoattract dendritic cells and macrophages but can also be expressed elsewhere under inflammatory conditions. Cxcl17-/- mice have lower numbers of macrophages or dendritic cells in mucosal tissues. CXCL17 is also able to chemoattract suppressor myeloid cells that can recruit regulatory T cells. To explore a possible role of Cxcl17 in T cells, we studied T cell populations from Cxcl17-/- or wild-type (WT) littermate mice. Cxcl17-/- mice have higher numbers of CD4+ and CD8+ T cells in spleen and lymph nodes (LNs). Upon activation, they produce higher levels of several proinflammatory cytokines and chemokines. Furthermore, a Cxcl17-/- mouse developed exacerbated disease in a T cell-dependent model of experimental autoimmune encephalomyelitis (EAE). By 18 days after immunization with myelin oligodendrocyte peptide, only 44% of Cxcl17-/- mice were still alive vs. 90% for WT mice. During EAE, Cxcl17-/- mice exhibited higher numbers of lymphoid and myeloid cells in spleen and LNs, whereas they had less myeloid cell infiltration in the CNS. Cxcl17-/- mice also had higher levels of some inflammatory cytokines in serum, suggesting that they may be involved in the poor survival of these mice. Abnormal T cell function may reflect altered myeloid cell migration, or it could be due to altered T cell development in the thymus. We conclude that CXCL17 is a novel factor regulating T cell homeostasis and function